Abstract:
Despite the continuing loss of wetland habitats and associated declines
in amphibian populations, attempts to translate wetland losses into
measurable losses to ecosystems have been lacking. We estimated the
potential productivity from the amphibian community that would be compromised
by the loss of a single isolated wetland that has been protected from
most industrial, agricultural, and urban impacts for the past 54 years.
We used a continuous drift fence at Ellenton Bay, a 10-ha freshwater
wetland on the Savannah River Site, near Aiken, South Carolina (U.S.A.),
to sample all amphibians for 1 year following a prolonged drought. Despite
intensive agricultural use of the land surrounding Ellenton Bay prior
to 1951, we documented 24 species and remarkably high numbers and biomass
of juvenile amphibians (>360,000 individuals; >1,400 kg) produced
during one breeding season. Anurans (17 species) were more abundant
than salamanders (7 species), comprising 96.4% of individual captures.
Most (95.9%) of the amphibian biomass came from 232095 individuals of
a single species of anuran (southern leopard frog [Rana sphenocephala]).
Our results revealed the resilience of an amphibian community to natural
stressors and historical habitat alteration and the potential magnitude
of biomass and energy transfer from isolated wetlands to surrounding
terrestrial habitat. We attributed the postdrought success of amphibians
to a combination of adult longevity (often >5years), a reduction
in predator abundance, and an abundance of larval food resources. Likewise,
the increaseof forest cover around Ellenton Bay from <20% in 1951
to >60% in 2001 probably contributed to the longterm persistence
of amphibians at this site. Our findings provide an optimistic counterpoint
to the issue of the global decline of biological diversity by demonstrating
that conservation efforts can mitigate historical habitatdegradation.